2000. Reverse Prefix of Word: AC

Author: tan-wei

src/solution/mod.rs

@@ -1507,3 +1507,4 @@ mod s1995_count_special_quadruplets;
 mod s1996_the_number_of_weak_characters_in_the_game;
 mod s1997_first_day_where_you_have_been_in_all_the_rooms;
 mod s1998_gcd_sort_of_an_array;
+mod s2000_reverse_prefix_of_word;

src/solution/s2000_reverse_prefix_of_word.rs

@@ -0,0 +1,90 @@
+/**
+ * [2000] Reverse Prefix of Word
+ *
+ * Given a 0-indexed string word and a character ch, reverse the segment of word that starts at index 0 and ends at the index of the first occurrence of ch (inclusive). If the character ch does not exist in word, do nothing.
+ *
+ * 	For example, if word = "abcdefd" and ch = "d", then you should reverse the segment that starts at 0 and ends at 3 (inclusive). The resulting string will be "<u>dcba</u>efd".
+ *
+ * Return the resulting string.
+ *  
+ * Example 1:
+ *
+ * Input: word = "<u>abcd</u>efd", ch = "d"
+ * Output: "<u>dcba</u>efd"
+ * Explanation: The first occurrence of "d" is at index 3.
+ * Reverse the part of word from 0 to 3 (inclusive), the resulting string is "dcbaefd".
+ *
+ * Example 2:
+ *
+ * Input: word = "<u>xyxz</u>xe", ch = "z"
+ * Output: "<u>zxyx</u>xe"
+ * Explanation: The first and only occurrence of "z" is at index 3.
+ * Reverse the part of word from 0 to 3 (inclusive), the resulting string is "zxyxxe".
+ *
+ * Example 3:
+ *
+ * Input: word = "abcd", ch = "z"
+ * Output: "abcd"
+ * Explanation: "z" does not exist in word.
+ * You should not do any reverse operation, the resulting string is "abcd".
+ *
+ *  
+ * Constraints:
+ *
+ * 	1 <= word.length <= 250
+ * 	word consists of lowercase English letters.
+ * 	ch is a lowercase English letter.
+ *
+ */
+pub struct Solution {}
+
+// problem: https://leetcode.com/problems/reverse-prefix-of-word/
+// discuss: https://leetcode.com/problems/reverse-prefix-of-word/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+impl Solution {
+    pub fn reverse_prefix(word: String, ch: char) -> String {
+        match word.split_once(ch) {
+            Some((pre, post)) => ch.to_string() + &pre.chars().rev().collect::<String>() + post,
+            None => word,
+        }
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2000_example_1() {
+        let word = "abcdefd".to_string();
+        let ch = 'd';
+
+        let result = "dcbaefd".to_string();
+
+        assert_eq!(Solution::reverse_prefix(word, ch), result);
+    }
+
+    #[test]
+    fn test_2000_example_2() {
+        let word = "xyxzxe".to_string();
+        let ch = 'z';
+
+        let result = "zxyxxe".to_string();
+
+        assert_eq!(Solution::reverse_prefix(word, ch), result);
+    }
+
+    #[test]
+    fn test_2000_example_3() {
+        let word = "abcd".to_string();
+        let ch = 'z';
+
+        let result = "abcd".to_string();
+
+        assert_eq!(Solution::reverse_prefix(word, ch), result);
+    }
+}